Friction clutches of this sort are known for example from DE 10 2005 003 505 A1. In general, such incorrect gaps are brought about over the operating life of the friction clutch through wear of the friction linings of the clutch plate and procedures setting the lining resiliency. An expedient way to compensate for wear is through compensating for the incorrect gap by setting the ideal axial spacing of the friction surfaces of the clutch relative to each other by twisting ramp/opposing ramp systems that operate on the circumference opposite each other in such a way that the desired spacing relationships are again produced between the actuating lever, which may take the form of a diaphragm spring, and a stop on the clutch cover.
When overtravel is used as the means of compensating for the incorrect gap, the friction clutch is operated by actuation beyond the engaged or disengaged state, by pressing or relaxing the actuating lever accordingly by the actuating system beyond such state. As that is done, the actuating lever lifts off of a device that blocks the ramp/opposing ramp system, so that the latter—usually supported by a corresponding power storage device—can compensate for the incorrect gap by turning the ramps contrary to the opposing ramps. The magnitude of the adjustment depends substantially on the position of the actuating lever. For this type of adjustment by producing overtravel, adjusting systems have proven especially advantageous which provide a device between the ramp/opposing ramp system and the actuating lever by means of which an adjustment is accomplished not by covering the entire overtravel but by adjusting in increments. To this end a so-called drive spring-worm gear device can be used, in which the overtravel and the resulting additional axial motion of the engagement bearing in the direction of disengagement, and the tilting of the actuating lever which in turn results, produces tangential travel of a tongue provided on the drive spring, which thereby jumps over a tooth of the worm gear wheel. At the next engagement procedure, the worm gear twists the ramp/opposing ramp system by a predefined amount. If the wear is greater than the amount adjusted by the engagement travel, the adjustment is repeated in the subsequent engagement procedures until the wear has been compensated for.
Typical actuating systems fulfill the function of axially displacing the actuating lever, by prescribing a defined engagement travel distance depending on the desired degree of frictional engagement between the clutch friction surfaces and the output-side friction linings for example of a clutch plate. In this connection, DE 10 2004 009 832 A1 reveals an actuation system in the form of a lever system in which a lever acts on the actuating lever through a roller bearing.